It is known from, for example, the published patent applications GB-2344405-A and GB-2410043-A to provide in a directional control valve a shear seal which consists of two cylindrical seals of which the rims bear against valve flanges that accommodate ports, the seals being urged apart by an intermediate compression spring, the seals and the spring being disposed in a transverse bore in a piston movable in a valve body.
One object of the invention is to provide an improved valve that provides a shear seal, particularly between a supply port and a function port. Another object of the invention is to provide a valve with seals, and in particular a shear seal, integral with a movable valve member. A further object of the invention is to provide a valve in which system pressure and the configuration of various seals combine to provide a ‘return’ force in a desired direction on a valve member.